1. Field of the Invention
The present invention is generally related to a panel annunciator mechanism and, more particularly, to an annunciator device which improves the efficiency of an annunciator and reduces reflective output from the annunciator when it is de-energized.
2. Description of the Prior Art
Many types of annunciators are known to those skilled in the art. It is common to use a light source in combination with a reflector to direct light toward a plate or membrane which has various indicia for the purpose of causing the light to pass through or around the indicia.
U.S. Pat. No. 4,288,672, which issued to Puccini on Sep. 8, 1981, discloses an illuminated keyboard apparatus which is useful in vehicle control panels. The illumination of key indicia is desired to facilitate identification and actuation of selected keys. The apparatus includes a housing for mounting key switches in a selected array with a frame disposed in the housing having key receiving apertures extending through a top of the frame. The frame is composed of light transmitting material and is arranged to transmit light from a light source mounted below the circuit board into and through the key identification indicia formed in a label disposed from the top of the frame.
U.S. Pat. No. 4,798,426, which issued to Malcolm et al on Jan. 17, 1989, describes a holographic optical element for use in an instrument panel display. The element is applied over existing aircraft panels and instruments so as to display an image which is reflected from a source located off the panel. The image is reflected only to an area at which the viewer may observe the image and is not directed to other areas so as to prevent unwanted reflection and glare within an aircraft cockpit.
U.S. Pat. No. 4,812,831, which issued to Laier on Mar. 14, 1989, discloses a key switch with a controllable illumination. An illuminated membrane keyboard includes a light beam matrix which, when broken by the shadow of a stylus, operates logic to turn on illumination for a preset time rendering a normally dead front appearing keyboard visible. This feature conserves energy that is required to power the illumination, lengthens the life of the illuminating source and limits access to the keyboard.
U.S. Pat. No. 4,851,624, which issued to Chestnut et al on Jul. 25, 1989, discloses a control assembly which has a panel illumination apparatus. The control assembly provides types of control elements such as switches and potentiometers carried in a housing. The housing includes an applique which has openings through which manual operating levers extend to operate the control elements. The applique includes labeling to indicate the functions being controlled. Lights are carried in the housing with the light emanating therefrom being directed to the openings for sharp illumination at the openings, in the levers and the labeling.
U.S. Pat. No. 3,793,514, which issued to Curl on Feb. 19, 1974, describes a panel lamp assembly for illuminating an instrument panel. It facilitates replacement of lamps and increases the amount of useful light from them, including a transparent housing located in a panel recess, a lamp assembly in the housing and a cap that can be screwed into the housing to hold the lamp assembly in place.
U.S. Pat. No. 3,799,647, which issued to Luft on Mar. 26, 1974, discloses a constant visibility electro-optic display. It has two coincident modes of operation, reflective and emissive. A partially silvered mirror reflects external ambient light and also passes light emitted from an internal source of back-lighting. The combined effects of the reflected and emitted light cause the contrast, and therefore the visibility of the display to be relatively constant even though the ambient light conditions may vary.
U.S. Pat. No. 3,800,135, which issued to Ramsey on Mar. 26, 1974, describes a fiber optic display panel illuminator. This device can be used in association with an automobile instrument panel and is formed with a reflective coded concave depression in an area where illumination of a legend or other device is required. The depression is slotted to afford insertion of a fiber optic ribbon which extends through the depression. The ribbon is remotely energized by a lamp to illuminate the depression. A clear plastic envelope for supporting the ribbon within the depression in assembled to the ribbon and the assembly is inserted into the slot from the rear of the instrument panel such that the slot holds the supporting envelope in place.
U.S. Pat. No. 4,532,395, which issued to Zukowski on Jul. 30, 1985, describes an electroluminescent flexible touch switch panel. The panel has a deformable membrane carrying a switch closure member and is provided with an overlying flexible electroluminescent laminated member providing light to the entire switch panel or selected areas thereof including lighting of keytop indicia on the flexible touch switches.
U.S. Pat. No. 4,376,879, which issued to Nagata et al on Mar. 15, 1983, describes a buttonless push switch board. It includes a plurality of push switches which comprises an insulator plate having a plurality of penetrating holes, a transparent flexible cover sheet overlying the main surface of the insulator sheet and identification marks printed thereon to indicate the position and functions of the switches. A transparent block is disposed in each hole of the insulator plate and is urged towards the cove plate by elastic members supported thereon. Each elastic member is cup shaped and has a movable contact corresponding to a pair of fixed contacts on the printed circuit plate. A lamp or a light emitting diode is disposed in each hole of the insulator plate and is mounted o the printed circuit.
U.S. Pat. No. 3,561,145, which issued to Shotwell on Feb. 9, 1971, describes a light distributing lens system for illuminating a display. It employs a tapered three dimensional wedge shaped panel member of substantially transparent material. It also employs a light source encased in a recess in the thicker base portion of the tapered wedge shaped panel member and an opaque frame intimately supporting the periphery of the tapered wedge-shaped panel member in a manner to obscure the light source from external view, but to permit the projection of light rays from the light source onto the display directly as well as indirectly through internal reflection from the entire first planar surface of the tapered wedge-shaped panel member.